Zen
About the Zen theme
Zen is the ultimate starting theme for Drupal. If you are building your own standards-compliant theme, you will find it much easier to start with Zen than to start with Garland or Bluemarine. This theme has LOTs of documentation in the form of code comments for both the PHP (template.php) and HTML (page.tpl.php, node.tpl.php).
Why should you use Zen? And why should you create your theme as a Zen sub-theme as opposed to just modifying an existing theme? Lots of reasons. You can also read several themer’s testimonials.
Besides this documentation, additional resources can be found…